Electromagnetic induction sensor, overlay member for electromagnetic induction sensor, and manufacturing method of electromagnetic induction sensor

ABSTRACT

Disclosed herein is an electromagnetic induction sensor that is used with a position indicator and includes coils for electromagnetic coupling with the position indicator. The electromagnetic induction sensor includes: a sensor board main body that includes an insulating substrate and a surface sheet attached to a side of a first surface of the insulating substrate, on which side a position is indicated by the position indicator; at least part of conductors forming the coils being formed on a second surface of the insulating substrate opposite from the first surface; and an overlay member that includes a magnetic powder material layer and is adhered to the side of the second surface of the sensor board main body.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority to Japanese Patent ApplicationNo. 2013-155204 filed on Jul. 26, 2013, the disclosure of which ishereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

Field of the Invention

The invention relates to an electromagnetic induction sensor, an overlaymember for an electromagnetic induction sensor, and a manufacturingmethod of an electromagnetic induction sensor.

Description of the Related Art

Position detecting devices of an electromagnetic induction system usedwith a pen-shaped position indicator have been widely used along withpopularization of so-called tablet terminals, pad portable terminals,and portable information devices called personal digital assistants(PDA). Furthermore, as the thickness of these electronic apparatusescontinues to be reduced, thickness of electromagnetic induction sensorsused in the position detecting devices of the electromagnetic inductionsystem is also reduced.

The electromagnetic induction sensor is electromagnetically coupled tothe pen-shaped position indicator to detect a position indicated by theposition indicator. For this purpose, the position indicator includes aresonant circuit composed of a coil and a capacitor to carry out theelectromagnetic coupling with the sensor. The electromagnetic inductionsensor includes a coil group to be electromagnetically coupled to theresonant circuit of the position indicator.

The electromagnetic induction sensor is formed of an electromagneticsheet member called a magnetic path plate, which is adhered to a sensorboard, as described in, for example, Patent Document 1 (Japanese PatentLaid-open No. 2009-3796). The electromagnetic sheet member is providedin order to allow utilization of magnetic flux generated from the sensorwith as little leakage as possible in electromagnetic coupling betweenthe sensor and a position indicator, and functions as an electromagneticshield between the sensor and the external.

The sensor is electromagnetically coupled to the position indicator todetect a position indicated by the position indicator in the detectionarea where the sensor accepts an input of position indication by theposition indicator. The detection area of the position indicator is set,for example, as a rectangular area and the position indicated by theposition indicator is detected as two-dimensional plane coordinates ofthe X-axis direction (horizontal direction) and the Y-axis direction(vertical direction).

FIGS. 10A and 10B show the configuration of a related-art sensor. Asshown in FIG. 10A, in a sensor board 10 configuring a sensor 1, anX-axis-direction loop coil group 12 is disposed on one surface side ofan insulating substrate 11 composed of, for example, polyethyleneterephthalate (PET), and a Y-axis-direction loop coil group 13 isdisposed on the other surface side. Furthermore, in the example of FIG.10A, for the sensor board 10, a surface sheet (overlay) 14 formed of,for example, a PET film is so formed as to cover the entirety of theX-axis-direction loop coil group 12, and a protective sheet (overlay) 15is so formed as to cover the entirety of the Y-axis-direction loop coilgroup 13.

The overlay is a layer of an insulating material used to wholly orpartially wrap and cover a conductor pattern formed on the externalsurface of a printed wiring board such as the sensor board 10 (See“Denshi Kairo Yougo (Electronic Circuit Terms and Definition)”JPCA-TD01-2008 Japan Electronics Packaging Circuits Association). In thepresent specification, a member that is or includes an overlay and isintegrally joined to (or formed with) a sensor board (a main body of asensor board, to be described later) to thereby form a sensor will bereferred to as an overlay member.

The overlay member configuring the surface sheet 14 and the overlaymember configuring the protective sheet 15 are formed by applying anadhesive (not shown) on one surface side of a PET film as the insulatingmaterial, for example. Via the adhesive, the overlay members (formed ofa PET film, for example) are so adhered to the sensor board 10 as tocover each of the X-axis-direction loop coil group 12 and theY-axis-direction loop coil group 13. The sensor board 10 is completedwhen the surface sheet 14 and the protective sheet 15 formed as theoverlay members are attached. In this example, a position indicator isso configured that a position indication input is made to the sensorboard 10 from the side of the surface sheet 14.

As shown in FIG. 10B, an electromagnetic sheet member 2 called amagnetic path plate includes a first layer 21 forming a magnetic pathmaterial and a second layer 22 for electromagnetic shielding. The firstlayer 21 forming the magnetic path material provides a magnetic path foran alternating magnetic field generated by a loop coil of the loop coilgroup 12 or 13 in connection with transmission and reception ofelectromagnetic waves, to thereby prevent diversion of the generatedmagnetic flux and to enhance the detection sensitivity of theelectromagnetic induction sensor 1 regarding the position indicator. Thesecond layer 22 for electromagnetic shielding performs a function toprevent an alternating magnetic field from being radiated to theexternal toward the side of the protective sheet 15 of theelectromagnetic induction sensor 1, and also to prevent electromagneticwaves from the external on the protective sheet 15 side from mixing, asnoise, into electromagnetic waves transmitted and received on the sideof the surface sheet 14.

As the first layer 21, a layer having high magnetic permeability isused. Specifically, in related arts, magnetic iron plates such as apermalloy plate and a silicon steel plate are used pursuant to recentdemands to reduce thickness of the electromagnetic induction sensors. Inparticular, recently, an amorphous alloy that has permeability as highas, for example, 1000 (H/m) and can be thinned to a thickness as smallas, for example, 25 microns is used as the first layer 21 of themagnetic path material. The second layer 22 is formed of a metalmaterial that is a non-magnetic material and has high electricalconductivity, for example, aluminum.

Because the amorphous alloy has extremely low electrical resistance, aneddy current is generated therein due to the magnetic flux applied tothe magnetic path material formed as the first layer 21. The eddycurrent acts to cancel the applied magnetic field. Even considering thedisadvantage associated with the generation of the eddy current, all inall the amorphous alloy having high permeability is considered as ahigh-performance magnetic path plate. Therefore, the amorphous alloy hasbeen used as the magnetic path material to form the first layer 21 thusfar.

The electromagnetic sheet member 2 is formed by adhering an aluminumlayer as the second layer 22 to a PET film 23 serving as a protectivelayer, and forming the first layer 21 composed of an amorphous alloy onthe second layer 22 composed of aluminum. Furthermore, in theelectromagnetic sheet member 2, an adhesive layer 24 is applied on thefirst layer 21 composed of the amorphous alloy.

The adhesive layer 24 of the electromagnetic sheet member 2 is bonded tothe protective sheet 15 of the sensor board 10. Then, as shown in FIG.11, the electromagnetic sheet member 2 is adhered to the sensor board10, so that the electromagnetic induction sensor 1 is formed. In thismanner, in the related art, the sensor board 10 and the electromagneticsheet member 2 are separately formed independent of each other and areadhered to each other, to thereby form the electromagnetic inductionsensor 1.

BRIEF SUMMARY

As described above, as the magnetic path material forming theelectromagnetic sheet member 2 in the related art, an amorphous alloy isused because of the characteristics that it has high magneticpermeability and can be thinned. The amorphous alloy is very hard and isnot easy to cut. Furthermore, the amorphous alloy, which has anon-crystalline structure, has large characteristic variation due todifficulty in manufacturing. In the related art, the characteristicvariation of the magnetic path material has been a large constraint onenhancement in the detection accuracy of the coordinates of a positionindicated by a position indicator on the electromagnetic inductionsensor 1.

Furthermore, because of the above-described characteristics of theamorphous alloy (e.g., the amorphous alloy being very hard), thefollowing fabrication method needs to be employed in the related art.Specifically, the amorphous alloy is so selected as to reduce thecharacteristic variation. The selected amorphous alloy must be cut by aspecial tool into a predetermined shape, which corresponds to the shapethat needs to be adhered to the sensor board 10. Then, to the cutamorphous alloy, the second layer 22 that is composed of aluminum andadhered to the protective layer 23 is adhered, so that theelectromagnetic sheet member 2 is pre-formed as a member separate fromthe sensor board 10.

Meanwhile, as shown in FIG. 11, the sensor board 10 is shaped into apredetermined final form including a lead part and so forth. Then, tothe sensor board 10 shaped into the predetermined final form, theelectromagnetic sheet member 2 including the amorphous alloy layer 21,which is shaped in conformity to the shape that needs to be adhered tothe sensor board 10 and is configured as a separate member, is alignedand bonded via the adhesive layer 24.

That is, in the related art, in view of the difficulty in cutting theamorphous alloy and the characteristic variation of the amorphous alloy,the electromagnetic induction sensor 1 needs to be formed by separatelypreparing (cutting) the sensor board 10 and preparing theelectromagnetic sheet member 2 and bonding the shaped (cut) sensor board10 and electromagnetic sheet member 2 to each other in accuratealignment.

However, the above-described step of bonding the sensor board 10 and theelectromagnetic sheet member 2 to each other is a large obstacle tomass-production of the electromagnetic induction sensor.

In view of the above points, an aspect of the invention is directed toovercoming the difficulty in manufacturing an electromagnetic inductionsensor and enabling enhancement in the detection accuracy of thecoordinates of a position indicated by a position indicator on theelectromagnetic induction sensor.

In order to solve the above-described problems, an embodiment of theinvention provides an electromagnetic induction sensor that is used witha position indicator and includes coils for electromagnetic couplingwith the position indicator. The electromagnetic induction sensorincludes a sensor board main body that includes an insulating substrateand a surface sheet adhered to the side of a first surface of theinsulating substrate on which side a position is indicated by theposition indicator. At least part of conductors forming the coils isformed on a second surface of the insulating substrate opposite from thefirst surface of the insulating substrate. The electromagnetic inductionsensor further includes an overlay member that has at least a magneticpowder material layer and that is adhered on the side of the secondsurface of the sensor board main body.

In the embodiment of the invention having the above-describedconfiguration, a magnetic powder material is used as a magnetic pathmaterial. The magnetic powder material is included in the overlay memberto cover the second surface side of the sensor board main body, on whichat least part of the coils for electromagnetic coupling with theposition indicator is formed. The overlay member is deposited on(adhered to) the sensor board main body on the second surface side tothereby form the electromagnetic induction sensor.

That is, the embodiment of the invention does not have a configurationlike the related art in which the electromagnetic induction sensor (orthe sensor board) and the magnetic path material are formed (cut-out) asseparate members and thereafter are bonded. Instead, the magnetic pathmaterial serves as part of the overlay member of the sensor that isintegrally formed with the sensor.

The reason why such configuration is possible is because the magneticpowder material layer composed of the magnetic powder material is usedas the magnetic path material. Specifically, the magnetic powdermaterial layer has lower hardness compared with the amorphous alloylayer of the related art and is easy to cut. Therefore, according to theembodiment of the invention, after the overlay member having at leastthe magnetic powder material layer is deposited on (adhered to) thesensor board main body, the entire (integral) assembly can be easilystamp-cut into a desired shape with a cutter. Thus, the manufacturingbecomes easy and the mass productivity is enhanced.

Furthermore, it is easy to form the magnetic powder material layer usingthe magnetic powder material while minimizing variation in thecharacteristics thereof. Therefore, according to the electromagneticinduction sensor of the embodiment of the invention, the detectionaccuracy of the coordinates of a position indicated by the positionindicator can be improved.

Moreover, the magnetic powder material can be made not as a goodconductor with low resistance like an amorphous alloy in the relatedart, but as a poor conductor specifically formulated to have highresistance by mixing in a resin. Thus, it is also possible to omit aninsulator layer between the second surface side of the sensor board mainbody and the magnetic powder material layer and instead to directlydeposit (adhere) the magnetic powder material layer on (to) the secondsurface side of the sensor board main body. In this case, because theinsulator layer between the second surface side of the sensor board mainbody and the magnetic powder material layer is unnecessary,correspondingly the thickness can be reduced.

According to the embodiment of the invention, it is possible to providean electromagnetic induction sensor that overcomes manufacturingdifficulty and enables enhancement in the detection accuracy of thecoordinates of a position indicated by a position indicator.

Furthermore, the electromagnetic induction sensor according to exemplaryembodiments of the invention is integrally formed, wherein the sensorboard main body integrally includes the magnetic path material. Thus,the adhesive layer (24 in FIG. 10B) used in the case of separatelyconfiguring the sensor board and the magnetic path material and joiningthem can be omitted in these embodiments, in addition to that theunnecessary overlay (15 in FIG. 10A) can be omitted. Therefore, thethickness of the electromagnetic induction sensor can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1C are sectional views of the structure of anelectromagnetic induction sensor according to an embodiment of theinvention;

FIG. 2 is a diagram of a position detecting circuit using theelectromagnetic induction sensor;

FIG. 3 is a diagram for explaining an overlay member that forms theelectromagnetic induction sensor according to the embodiment of theinvention;

FIGS. 4A and 4B are diagrams for explaining the overlay member thatforms the electromagnetic induction sensor according to the embodimentof the invention;

FIG. 5 is a table explaining a magnetic path material used in theelectromagnetic induction sensor according to the embodiment of theinvention in comparison to a related art;

FIG. 6 is a diagram of one example of a manufacturing method of theelectromagnetic induction sensor according to an embodiment of theinvention;

FIGS. 7A to 7C are diagrams of another example of the overlay memberforming the electromagnetic induction sensor according to an embodimentof the invention;

FIGS. 8A to 8D are sectional views of the structure of anelectromagnetic induction sensor according to another embodiment of theinvention;

FIGS. 9A to 9E are sectional views of part of the structures ofelectromagnetic induction sensors according to further embodiments ofthe invention;

FIGS. 10A and 10B are sectional views of one example of the structure ofan electromagnetic induction sensor of the related art; and

FIG. 11 is a diagram of an example of a manufacturing method of theelectromagnetic induction sensor of the related art.

DETAILED DESCRIPTION

Electromagnetic induction sensors and manufacturing methods thereofaccording to embodiments of the invention will be described below withreference to the drawings.

First Embodiment

FIGS. 1A to 1C are sectional views showing a configuration example of anelectromagnetic induction sensor according to a first embodiment of theinvention. An electromagnetic induction sensor 3 of the first embodimentis composed of a sensor board main body 31 shown in FIG. 1A and anoverlay member 32 shown in FIG. 1B. The sensor 3 is integrally formed bydepositing (adhering) the overlay member 32 on (to) the sensor boardmain body 31 (see FIG. 1C).

As shown in FIG. 1A, in the sensor board main body 31, anX-axis-direction loop coil group conductor 312 is disposed on onesurface side of an insulating substrate 311 composed of, for example,PET and a Y-axis-direction loop coil group conductor 313 is disposed onthe other surface side opposite from the one surface. Furthermore, inthe example of FIG. 1A, a surface sheet (overlay) 314 formed of, forexample, a PET film is so deposited (adhered) as to cover theX-axis-direction loop coil group conductor 312 as a whole. A positionindicator is so configured that a position indication input is made tothe sensor board main body 31 from the side of the surface sheet 314.

With reference to FIG. 2, an explanation will be made about aconfiguration to detect a position indicated by the position indicatorby the X-axis-direction loop coil group conductor 312 and theY-axis-direction loop coil group conductor 313 provided in the sensorboard main body 31. A position indicator 4, which is used with theelectromagnetic induction sensor 3 including the sensor board main body31, includes a resonant circuit composed of a coil 4L and a capacitor 4Cconnected in parallel to the coil 4L, as shown in FIG. 2.

As shown in FIG. 2, in the sensor board main body 31, plural rectangularX-axis-direction loop coils 312X forming the X-axis-direction loop coilgroup conductor 312 are arranged at equal intervals and to sequentiallyoverlap with each other in the horizontal direction (X-axis direction)of the detection area of the indicated position by the positionindicator 4. Furthermore, plural rectangular Y-axis-direction loop coils313Y forming the Y-axis-direction loop coil group conductor 313 arearranged at equal intervals and to sequentially overlap with each otherin the vertical direction (Y-axis direction) perpendicular to thehorizontal direction of the detection area of the indicated position bythe position indicator 4. In this example, n X-axis-direction loop coils312X are disposed in the X-axis direction and m Y-axis-direction loopcoils 313Y are disposed in the Y-axis direction.

A sensor circuit part is provided in the sensor 3. The sensor circuitpart includes a selection circuit 101, an oscillator 102, a currentdriver 103, a transmission/reception switch circuit 104, a receivingamplifier 105, a detection circuit 106, a low-pass filter 107, asample/hold circuit 108, an analog-to-digital (A/D) conversion circuit109, and a processing controller 110.

Each of the plural X-axis-direction loop coils 312X and each of theplural Y-axis-direction loop coils 313Y are connected to the selectioncircuit 101. The selection circuit 101 sequentially selects one loopcoil among the plural X-axis-direction loop coils 312X and the pluralY-axis-direction loop coils 313Y in accordance with a controlinstruction from the processing controller 110.

The oscillator 102 generates an AC signal with a frequency f0. The ACsignal is supplied to the current driver 103 to be converted to acurrent and then sent out to the transmission/reception switch circuit104. The transmission/reception switch circuit 104 switches theconnection target (a transmission-side terminal T or a reception-sideterminal R), to which the loop coil 312X or 313Y selected by theselection circuit 101 is connected, every predetermined time undercontrol by the processing controller 110. The current driver 103 isconnected to the transmission-side terminal T and the receivingamplifier 105 is connected to the reception-side terminal R.

Therefore, at the time of transmission, the AC signal from the currentdriver 103 is supplied to the loop coil 312X or 313Y selected by theselection circuit 101 via the transmission-side terminal T of thetransmission/reception switch circuit 104. At the time of reception, aninduced voltage generated in the loop coil 312X or 313Y selected by theselection circuit 101 is supplied to the receiving amplifier 105 via theselection circuit 101 and the reception-side terminal R of thetransmission/reception switch circuit 104 to be amplified and sent outto the detection circuit 106.

The signal detected by the detection circuit 106 is supplied to the A/Dconversion circuit 109 via the low-pass filter 107 and the sample/holdcircuit 108. The A/D conversion circuit 109 converts an analog signal toa digital signal and supplies it to the processing controller 110.

The processing controller 110 carries out control for positiondetection. Specifically, the processing controller 110 controls theselection of the loop coil 312X or 313Y in the selection circuit 101,signal switch control in the transmission/reception switch circuit 104,the timing of the sample/hold circuit 108, and so forth.

The processing controller 110 switches the transmission/reception switchcircuit 104 to make a connection to the transmission-side terminal T tothereby carry out energization control of the loop coil 312X or 313Yselected by the selection circuit 101 and to make the selected coil sendout electromagnetic waves (or generate an alternating magnetic field).The resonant circuit composed of the coil 4L and the capacitor 4C in theposition indicator 4 receives the electromagnetic waves sent out fromthe loop coil 312X or 313Y (or obtains an induced electromotive forcefrom the generated alternating magnetic field) to store energy.

Next, the processing controller 110 switches the transmission/receptionswitch circuit 104 to make a connection to the reception-side terminalR. Then, an induced voltage is generated in the respective loop coils312X and 313Y of the X-axis-direction loop coil group conductor 312 andthe Y-axis-direction loop coil group conductor 313 by electromagneticwaves transmitted from the position indicator 4. Based on the level ofthe voltage value of the induced voltage generated in the respectiveloop coils 312X and 313Y, the processing controller 110 calculates thecoordinate values of an indicated position by the position indicator 4in the detection area of the sensor 3 along the X-axis direction and theY-axis direction.

Next, the overlay member 32 will be described. As shown in FIG. 1B, theoverlay member 32 includes an overlay base film 321 that is composed ofan insulator material, for example, PET, on which an adhesive 322 isapplied on the side of one surface 321 a. A magnetic powder materiallayer 323 is deposited on the other surface 321 b of the overlay basefilm 321, on which surface the adhesive 322 is not applied. The magneticpowder material layer 323 provides a magnetic path material that forms amagnetic path for an alternating magnetic field generated by theX-axis-direction loop coils 312X and the Y-axis-direction loop coils313Y of the sensor board main body 31.

In this example, the magnetic powder material layer 323 is formed of amaterial obtained by mixing powder of a magnetic material having highmagnetic permeability, such as powder of an amorphous alloy, with anon-magnetic, non-conductive polymer material, such as resin in thisexample. In this embodiment, the magnetic powder material is provided inthe form of a coating material and the magnetic powder material in thecoating-material form is applied over the other surface 321 b of theoverlay base film 321, on which surface the adhesive 322 is not applied,to thereby create the magnetic powder material layer 323.

FIG. 3 shows one example of the method for applying the magnetic powdermaterial layer 323 on the overlay base film 321.

As shown in FIG. 3, the overlay base film 321 is wound around a supplyreel 33S and the overlay base film 321 run out from the supply reel 33Sis rewound by a take-up reel 33T after the magnetic powder materiallayer 323 is applied on its one surface side. An application apparatus34 of the magnetic powder material layer 323 is provided in the middleof the conveyance route of the overlay base film 321 between the supplyreel 33S and the take-up reel 33T. The application apparatus 34 includesa reservoir 342 of a magnetic powder paste 341. In addition, althoughdescription of a detailed configuration is omitted, the applicationapparatus 34 includes an application part 343 that applies the magneticpowder paste 341 in the reservoir 342 over the overlay base film 321 toa thickness of, for example, 50 to 100 μm.

The magnetic powder paste 341 is a material formed into a paste form(glue form) by mixing the above-described magnetic powder materialcomposed of, for example, powder of an amorphous alloy with anon-magnetic, non-conductive polymer material composed of, for example,resin. In this example, each magnetic powder piece 341P contained in themagnetic powder material has a flattened shape (see FIG. 3: in FIG. 3,the magnetic powder piece 341P has a flattened elliptical shape).

In this example, in the movement route between the application apparatus34 and the take-up reel 33T, a magnetic field generating apparatus 35 isprovided for aligning the magnetization directions of the magneticpowder pieces 341P contained in the magnetic powder paste 341 to adirection parallel to the film surface of the overlay base film 321,i.e., to a direction perpendicular to the thickness direction of themagnetic powder material layer 323.

In this example, the magnetic field generating apparatus 35 includes arun-through space 351, through which the overlay base film 321 passes,on which the magnetic powder paste 341 has been applied by theapplication apparatus 34 to form the magnetic powder material layer 323.The magnetic field generating apparatus 35 is so configured as togenerate, in its run-through space 351, a magnetic field 35F that is ina direction parallel to the film surface of the overlay base film 321(i.e., a direction perpendicular to the thickness direction of themagnetic powder material layer 323). It is to be noted that, in thisexample, the magnetic field generating apparatus 35 generates themagnetic field 35F in a direction parallel to the film surface of theoverlay base film 321 and along the extension direction of the film.

The double-headed arrow 35F in the diagram indicates that the magneticfield may be in either orientation as long as the vector of theorientation is in a direction perpendicular to the thickness direction.This means that reversal of the magnetic poles is permitted as long asthe N-pole is oriented in either one of the arrow heads and the S-poleis oriented in the other arrow head, as the magnetization directions ofa magnetic material or a soft magnetic material.

At a position surrounded by a dotted circle mark 36 a in FIG. 3, whichis a position before the passage through the magnetic field generatingapparatus 35, the flattened surface of each of the flattened magneticpowder pieces 341P contained in the magnetic powder material layer 323formed by applying the magnetic powder paste 341 on the overlay basefilm 321 in the application apparatus 34 is oriented in a randomdirection, as shown at the lower left part in FIG. 3.

Upon passing through the magnetic field 35F in the run-through space 351of the magnetic field generating apparatus 35, the magnetic powder piece341P contained in the magnetic powder material layer 323 is magnetizedby the magnetic field 35F and magnetic poles are generated at both endsin the major radius direction of the flattened elliptical shape. Thus,the magnetic powder piece 341P is so moved (or oriented) that itsmagnetization direction, which is the direction of the line coupling thegenerated magnetic poles at both ends, becomes the same as the directionof the magnetic field 35F. Specifically, at a position surrounded by adotted circle mark 36 b in FIG. 3, which is a position after the passagethrough the magnetic field generating apparatus 35, the flattenedsurface of each of the magnetic powder pieces 341P contained in themagnetic powder material layer 323 formed on the overlay base film 321is so moved as to become parallel to the direction of the magnetic field35F, so that all the magnetic powder pieces 341P are aligned, as shownin an enlarged diagram at the lower right part in FIG. 3.

This will be further explained with reference to FIGS. 4A and 4B. FIGS.4A and 4B are diagrams showing the magnetization directions of themagnetic powder pieces 341P in the magnetic powder material layer 323before and after the passage through the magnetic field generatingapparatus 35. FIGS. 4A and 4B are schematic diagrams for explaining thatthe magnetization direction of the magnetic powder piece 341P is changedbetween before and after the magnetic field generating apparatus 35. Itshould be apparent to those skilled in the art that the depictedrelationship between the size of the magnetic powder piece 341P havingthe flattened elliptical shape and the thickness and width of themagnetic powder material layer 323 may be different from the actualrelationship.

Specifically, FIG. 4A is a diagram for explaining the magnetizationdirections of the magnetic powder pieces 341P (directions of the linecoupling the magnetic poles) when the magnetic powder material layer 323formed on the overlay base film 321 is viewed from the directionperpendicular to the film surface of the overlay base film 321. FIG. 4Bis a diagram for explaining the magnetization directions of the magneticpowder pieces 341P (directions of the line coupling the magnetic poles)when the magnetic powder material layer 323 is viewed from a directionperpendicular to its thickness direction.

As shown in FIGS. 4A and 4B, due to the passage through the magneticfield generating apparatus 35, the magnetization direction of each ofthe magnetic powder pieces 341P contained in the magnetic powdermaterial layer 323 formed on the overlay base film 321 (directionsubstantially along with the major axis of a flattened elliptical shapeshown by the arrow given to each magnetic powder piece 341P in FIG. 4A)is aligned with the same direction as that of the magnetic field 35F,which is in a direction perpendicular to the thickness direction of themagnetic powder material layer 323.

As shown in FIG. 4B, the magnetization directions of all the magneticpowder pieces 341P contained in the magnetic powder material layer 323are aligned with a direction parallel to the film surface of the overlaybase film 321. This can facilitate preventing magnetic flux leakage fromthe magnetic powder material layer 323. Furthermore, this makes it easyto control the permeability of the magnetic powder material layer, andalso to control the thickness of the magnetic powder material layer toachieve optimum permeability.

In the above-described example, the direction of the magnetic field 35Fis a direction parallel to the film surface of the overlay base film 321and is a direction along the extension direction of the film, which isthe conveyance direction of the overlay base film 321 when the magneticpowder material layer 323 is formed as shown in FIG. 4A. Therefore, themagnetization directions of the magnetic powder pieces 341P contained inthe magnetic powder material layer 323 are also aligned with a directionparallel to the film surface of the overlay base film 321 and adirection along the extension direction of the film. However, it is notnecessary for all of the magnetization directions of the magnetic powderpieces 341P to be aligned with the same direction, as long as they areeach aligned with a direction parallel to the film surface of theoverlay base film 321.

It should be apparent to those skilled in the art that the flattenedshape of the magnetic powder piece 341P is not limited to the ellipticalshape as depicted above. It may be any shape as long as themagnetization direction can be kept as a direction perpendicular to thethickness direction while the magnetization direction is permitted toreverse its polarities. Typically, the shape may be a needle shape or abar shape. For example, the magnetic powder may be a soft magneticmaterial having such a shape that a vector component (primary component)in a certain direction is larger than other vector componentsperpendicular to this direction. In some embodiments, the primary vectorcomponents of a myriad of magnetic powder pieces 341P as statisticallymeasured are aligned with a direction perpendicular to the thicknessdirection.

In the overlay member 32 of this example, the magnetic powder materiallayer 323 is formed on the overlay base film 321 in the above-describedmanner and the adhesive layer 322 is deposited on the other surface ofthe overlay base film 321, on which the magnetic powder material layer323 is not formed. An electromagnetic shield layer 324 is deposited on(adhered to) the magnetic powder material layer 323 and a protectivesheet 325 is deposited on (adhered to) the electromagnetic shield layer324. Thereby, the overlay member 32 is configured.

As described above, in the related art, an amorphous alloy with highpermeability as the magnetic path material is used as a single(independent) material. The amorphous alloy has high hardness and thushas poor processability. Therefore, the component including the magneticpath material needs to be configured (cut) as an independent memberseparate from the sensor board using external shape processing inadvance, and thereafter the cut magnetic path material needs to beadhered to the sensor board, to which the overlay member has alreadybeen adhered. That is, it is very laborious and practically difficult toadhere the magnetic path material composed of an amorphous alloy withpoor processability to the overlay member serving as part of the sensor.

In contrast, in the present embodiment, the magnetic powder materiallayer 323 obtained by mixing powder of a magnetic material having highpermeability with a polymer material is used as the magnetic pathmaterial. Consequently, the magnetic powder material can be formed as,for example, a coating material as described above, and can be adhered(applied) to the overlay base film 321 in advance to thereby form theoverlay member 32, which in turn will integrally form part of the sensor3.

In addition, as described above, the magnetic powder pieces contained inthe magnetic powder material layer 323 formed in the overlay member 32have a flattened shape and their magnetization directions are alignedwith a direction parallel to the film surface of the overlay base film321 of the overlay member 32 (direction perpendicular to the thicknessdirection of the magnetic powder material layer 323). This makes it easyto prevent magnetic flux from leaking in the thickness direction(direction perpendicular to the plane surface) and to control thepermeability and the thickness of the magnetic powder material layer 323in the overlay member 32.

The method for adhering the magnetic powder material layer 323 onto theoverlay base film 321 is not limited to the method in which the magneticpowder material is formed as a coating material. For example, it is alsopossible to employ a configuration in which the magnetic powder materialis impregnated with an adhesive and the magnetic powder material layer323 is deposited on the overlay base film 321 and is bonded thereto bythe adhesive.

As the magnetic powder material to form the magnetic powder materiallayer 323, powder of permalloy or ferrite (iron oxide) can also be usedinstead of powder of an amorphous alloy. Furthermore, the polymermaterial is not limited to resin and may be either an organic polymermaterial or an inorganic polymer material. For example, as the organicpolymer material, a natural polymer material such as protein, nucleicacid, polysaccharides (cellulose, starch, etc.), and natural rubber anda synthetic polymer material such as synthetic resin, silicone resin,synthetic fiber, and synthetic rubber can be used. As the inorganicpolymer material, a natural polymer material such as silicon dioxide(crystal and quartz), mica, feldspar, and asbestos and a syntheticpolymer material such as glass and synthetic ruby can be used.

In the overlay member 32, the electromagnetic shield layer 324 isadhered to a surface of the magnetic powder material layer 323. In thisexample, the electromagnetic shield layer 324 is formed of a metalmaterial, which is a non-magnetic material. The metal material has lowresistance (preferably almost zero electrical resistance) and highelectrical conductivity in order to generate an eddy currentcorresponding to the alternating magnetic field from theX-axis-direction loop coils 312X and the Y-axis-direction loop coils313Y of the sensor board main body 31, so that the alternating magneticfield may be prevented from leaking to the external. In this example,the electromagnetic shield layer 324 is formed of aluminum.

As the method for attaching (adhering) the electromagnetic shield layer324 composed of aluminum on (to) the magnetic powder material layer 323,besides a method of bonding with an adhesive, for example, a method ofpressure bonding or a method of vapor-depositing aluminum on themagnetic powder material layer 323 can be used. In the case of themethod of pressure bonding, the magnetic powder material layer 323 maybe impregnated with an adhesive.

Furthermore, in the overlay member 32, the protective sheet 325 composedof an insulator such as PET is attached to the electromagnetic shieldlayer 324 by, for example, an adhesive (not shown). The protective sheet325 ensures insulation between the sensor 3 and electronic parts on aprinted wiring board or the like disposed on the side of the protectivesheet 325 of the sensor 3.

In the sensor 3 configured in the above-described manner, the magneticpowder material layer 323 of the magnetic path material has lowerpermeability and higher electrical resistance compared with a layercomposed only of a high-permeability material such as an amorphousalloy, because powder of a high-permeability material such as anamorphous alloy is mixed with a non-magnetic, non-conductive polymermaterial. Furthermore, it has lower hardness than the amorphous alloyand therefore cutting it is easy.

However, compared with the thickness of the amorphous alloy sheet, whichis as small as, for example, 25 μm, the thickness of the magnetic powdermaterial layer 323 may be slightly larger, for example, about 50 to 100μm. Nonetheless, in accordance with various embodiments, the magneticpowder material layer 323 is applied to form the overlay member 32 thatis integrally formed as part of the sensor 3 in advance. That is,differently from the related art, it is not necessary to form (cut out)the electromagnetic sheet member as a separate member and bond it to thesensor board (10 in FIGS. 10A-11), to which an overlay 15 is alreadyadhered via an adhesive (not shown in FIG. 10A). Instead, according toembodiments of the present invention, the overlay member 32 includingthe magnetic powder material layer 323 is integrally formed with thesensor board main body 31. Thus, there is no need to provide the overlay(protective sheet) 15, on which an adhesive is applied, and to bond theoverlay 15, via the adhesive, to the sensor board 10. Correspondingly,the thickness of the sensor board can be reduced. Therefore, even whenthe thickness of the magnetic powder material layer 323 is larger thanthat of the amorphous alloy sheet, a thickness equivalent to that of theprior art sensor can be achieved for the sensor 3 as a whole includingthe magnetic path material (323) and the electromagnetic shield material(324).

FIG. 5 compares the characteristics of the first layer 21 of theelectromagnetic sheet member 2 of Patent Document 1 discussed in thebackground section above, i.e., the magnetic path material (amorphousalloy), and the characteristics of the magnetic powder material layer323 of the present embodiment. As shown in FIG. 5, the magneticpermeability of the first layer (amorphous alloy) of Patent Document 1is as high as 1000 [H/m] and thus the first layer provides highperformance as the magnetic path for the alternating magnetic field,whereas its electrical resistance is very low. Therefore, as describedabove, because the electrical resistance is extremely low, the magneticpath material composed of an amorphous alloy has a weakness that an eddycurrent is generated due to the magnetic flux applied to the magneticpath material and the eddy current acts to cancel the applied magneticfield. Furthermore, the magnetic path material of an amorphous alloy hashigh hardness and therefore has a problem of poor processabilityalthough being excellent in terms of thinness.

In contrast, the magnetic powder material layer 323 of the embodimenthas low permeability of about 50 to 240 [H/m] but has a large electricalresistance value of, for example, 100 kΩ, because it is obtained bymixing powder of a magnetic material with a non-magnetic, non-conductivepolymer material. Thus, the eddy current that may be generated by thealternating magnetic field is greatly suppressed. Therefore, thealternating magnetic flux can avoid the influence attributed to the eddycurrent. This allows the magnetic powder material layer 323 to form adesirable magnetic path although its permeability is low.

Therefore, the magnetic powder material layer 323 provides sufficientlyhigh performance as a magnetic flux path for the alternating magneticfield generated by the X-axis-direction loop coils 312X and theY-axis-direction loop coils 313Y and the alternating magnetic fieldreceived from the position indicator. This can favorably maintain thesensitivity of the sensor 3.

However, if the thickness of the magnetic powder material layer 323 ofthe present embodiment is small, possibly, part of the alternatingmagnetic field generated by the X-axis-direction loop coils 312X and theY-axis-direction loop coils 313Y and the alternating magnetic fieldreceived from the position indicator may pass through (penetrate) themagnetic powder material layer 323 to leak to the side of the sensor 3opposite from the surface sheet 314 (i.e., toward the bottom side inFIG. 1C). In the present embodiment, such leakage of the alternatingmagnetic flux is blocked by disposing the electromagnetic shield layer324 composed of, for example, aluminum on the magnetic powder materiallayer 323 and combining it with the magnetic powder material layer 323in the overlay member 32.

Specifically, the alternating magnetic flux leakage from the magneticpowder material layer 323 is allowable but the leaked alternatingmagnetic flux is prevented from further leaking from the electromagneticshield layer 324 to the external due to an eddy current generated in theelectromagnetic shield layer 324 having electrical conductivity.Therefore, even when there is an alternating magnetic field leaked fromthe magnetic powder material layer 323, further leakage to the sideopposite from the magnetic powder material layer 323 across (through)the electromagnetic shield layer 324 is prevented. Thus, the alternatingmagnetic flux due to the alternating magnetic field generated by theX-axis-direction loop coils 312X and the Y-axis-direction loop coils313Y and the alternating magnetic field received from the positionindicator is prevented from leaking to the external of the sensor 3based on the configuration in which the magnetic powder material layer323 and the electromagnetic shield layer 324 are combined.

Furthermore, entry of electromagnetic noise from the external of thesensor 3 is prevented by the eddy current generated in theelectromagnetic shield layer 324. The material of the electromagneticshield layer 324 is not limited to aluminum. For example, magnesiumalloy, stainless steel (SUS), copper, and alloy thereof (brass etc.) canalso be used.

When the magnetic powder material layer 323 has a certain degree ofthickness, leakage of the alternating magnetic field is small.Therefore, if a noise generation source such as an electronic circuitdoes not exist under the sensor 3, it may not be necessary to arrangethe electromagnetic shield layer 324. In this case, a configurationequivalent to those shown in FIGS. 7A to 7C and 9E can be used.

The magnetic powder material layer 323 in the sensor 3 of the presentembodiment has relatively low hardness and is excellent inprocessability because it is obtained by mixing powder of a magneticmaterial with a non-magnetic, non-conductive polymer material. Theelectromagnetic shield layer 324 also has relatively low hardness and isexcellent in processability. Therefore, by utilizing these advantagesand employing a configuration in which the magnetic powder materiallayer 323 and the electromagnetic shield layer 324 are formed in theoverlay member 32 in advance, the following manufacturing method of thesensor 3 to be described below in reference to FIG. 6 can be employed,which allows for mass production of the sensor 3.

In some cases the thickness of the magnetic powder material layer 323 islarger than that of the amorphous alloy layer 21 of the related art, asdiscussed above. However, the magnetic path material 323 is deposited(applied) in the overlay member 32, which is integrally formed as partof the electromagnetic induction sensor 3, according to exemplaryembodiments of the invention. Therefore, because variouscomponents/layers are integrally formed, it becomes unnecessary to useadhesive layers previously used in the related art to bond togethervarious components/layers that are separately formed in advance, such asan adhesive layer used to bond the protective sheets (14, 15 in FIG.10A) to the rest of the components/layers. Correspondingly, thethickness of the sensor 3 can be reduced.

Embodiment of Manufacturing Method of Sensor 3

FIG. 6 is a diagram for explaining a manufacturing method of the sensor3 according to an embodiment of the present invention. As shown in FIG.6, in this example, the overlay member 32 is formed into a sheet shape.Then, an overlay member roll 32L obtained by winding a predeterminedlength of the overlay member sheet 32S is prepared. The overlay membersheet 32S is a component obtained by adhering release paper 326 to theadhesive layer 322, which is in turn adhered to the one surface 321 a ofthe overlay base film 321 in the overlay member 32 having theconfiguration shown in FIG. 1B.

As shown in FIG. 6, the overlay member sheet 32S drawn out from theoverlay member roll 32L is in the state in which the adhesive layer 322is exposed when the release paper 326 is peeled off.

The X-axis-direction loop coil group conductors 312 and theY-axis-direction loop coil group conductors 313 are formed on the frontand back surfaces of the insulating substrates 311 and the surface sheet314 is adhered (applied) to form the sensor board main bodies 31 (seeFIG. 1A). In this case, although being subjected to external shapeprocessing (cutting), the sensor board main bodies 31 (as shown in FIG.6) do not need to be processed into a final outer shape with highaccuracy and are formed into parts having some dimensional tolerance ormargin. However, although not shown in FIG. 6, a position reference markuseful for processing into final outer shape dimensions with highaccuracy is formed on each of the sensor board main bodies 31 in anexternally recognizable form.

Then, the sensor board main bodies 31 formed in the above-describedmanner are disposed on the adhesive layer 322 of the overlay membersheet 32S with the side of the Y-axis-direction loop coil groupconductors 313 made to face the adhesive layer 322, and are bonded tothe overlay member sheet 32S. At this time, in reference to theabove-described position reference mark, alignment is so performed thatthe overlay member 32 comes to have a predetermined positionalrelationship with the sensor board main body 31.

Then, in the present embodiment of the manufacturing method, the sensorboard main bodies 31 deposited on the overlay member sheet 32S areconveyed to below a cutter (not shown) to undergo stamping processingaccording to the final outer shape of the sensor 3. After alignment isperformed with respect to the cutter for stamping processing inreference to the position reference mark, stamp-cutting processing isperformed by the cutter so that the sensor board main bodies 31 adheredto the overlay member sheet 32S may be formed into the final outershape. Thereby, the sensors 3 are formed, in which the overlay members32 are adhered to the sensor board main bodies 31.

In this case, if plural cutters for stamping processing are arranged inparallel, plural sensors 3 can be simultaneously manufactured.

In the above-described manner, in the manufacturing method of a sensoraccording to the present embodiment, the sensor 3 can be manufactured bysimpler steps as compared with the related art. Specifically, in therelated art, the sensor needs to be manufactured as follows. The sensorboard and the electromagnetic sheet member are separately fabricated toseparately undergo outer shape processing (e.g., cutting). Thereafter,the step of bonding the cut sensor board to the cut electromagneticsheet member is carried out. Therefore, the manufacturing steps arecomplicated and mass production is difficult.

In contrast, according to the manufacturing method of a sensor in thepresent embodiment, the sensors 3 can be manufactured by very simplesteps of fabricating the sensor board main bodies 31, depositing(adhering) the fabricated sensor board main bodies 31 on (to) theoverlay member sheet 32S prepared in advance, and performing stampingprocessing to the main bodies 31 combined with the overlay member sheet32S. In addition, in this case, in contrast to the related art in whicha special cutting step is required for the electromagnetic sheet memberbecause of hardness of the amorphous alloy used as the magnetic pathmaterial, stamping processing can be easily performed by using astamp-cutter because the magnetic path material is formed by a magneticpowder material layer. Therefore, the manufacturing method is suitablefor mass production.

Furthermore, in the sensor 3 of the present embodiment, the magneticpowder material whose permeability is not as high as that of anamorphous alloy is used as the magnetic path material. Therefore, evenwhen a geomagnetic sensor (Hall element or the like) that detects DCmagnetic flux due to a DC magnetic field such as the geomagnetism islocated outside the protective sheet 325 of the sensor 3, thegeomagnetism can be accurately sensed.

Specifically, when the geomagnetic sensor is provided near the sensorthat uses a high-permeability material such as an amorphous alloy as itsmagnetic path material, in the case of a DC magnetic field such as thegeomagnetism, possibly the direction of the DC magnetic flux is changedto pass through the magnetic path material with high permeability andthus the correct direction of the geomagnetism cannot be detected by thegeomagnetic sensor.

In contrast, in the sensor 3 of the present embodiment, the permeabilityof the magnetic powder material forming the magnetic powder materiallayer 323 can be adjusted to a desired permeability level by adjustingthe mixing ratio between the powder of a high-permeability material suchas an amorphous alloy and a polymer material. For example, thepermeability can be ideally suppressed so that DC magnetic flux due to aDC magnetic field such as the geomagnetism may be essentially preventedfrom being distorted by the magnetic powder material layer. Moreover, itis also relatively easy to fabricate the magnetic powder material havinga desired electrical resistance for the purpose of suppressing a currentflow through the magnetic powder material layer 323.

In the above-described first embodiment, the overlay member 32 isconfigured to include not only the magnetic powder material layer 323but also the electromagnetic shield layer 324. However, theelectromagnetic shield layer 324 need not be provided depending on eachapplication condition such as the particular ambient environment of theplace where the electromagnetic induction sensor 3 is set. When theelectromagnetic shield member 324 is omitted, to the sensor board mainbody 31 shown in FIG. 7A (which is the same as 31 in FIG. 1A), anoverlay member 32′ obtained by removing the electromagnetic shield layer324 from the overlay member 32 of FIG. 1B is attached as shown in FIG.7B. This results in formation of a sensor 3′ shown in FIG. 7C.

Second Embodiment

In the above-described first embodiment, with respect to theY-axis-direction loop coil group conductor 313 of the sensor board mainbody 31, the magnetic powder material layer 323 is deposited(adhered/applied) with the intermediary of an insulating layer formed ofthe overlay base film 321. However, because the magnetic powder materiallayer 323 has resistance as high as 100 kΩ as shown in the table of FIG.5, even when the insulating layer formed of the overlay base film 321 isnot provided, there may be practically no influence on the electricalcharacteristics of the Y-axis-direction loop coil group conductor 313.Thus, the overlay base film 321 may be omitted. By employing theconfiguration in which the insulating layer formed of the overlay basefilm 321 is not provided, a sensor can be realized whose thickness iseven smaller than that of the sensor 3 of the first embodiment.

The second embodiment provides an electromagnetic induction sensorhaving such configuration. The same parts as those included in thesensor 3 of the first embodiment are given the same reference numeralsand detailed description thereof is omitted.

FIGS. 8A to 8D are diagrams for explaining an electromagnetic inductionsensor 5 of the second embodiment and a manufacturing method therefor.

In the second embodiment, first, the sensor board main body 31 is formedjust as with the first embodiment as shown in FIG. 8A. Next, as shown inFIG. 8B, a magnetic powder material layer 327 is formed to cover theentirety of the Y-axis-direction loop coil group conductor 313 formed ona surface of the insulating substrate 311 of the sensor board main body31 on the side opposite from the surface sheet 314.

The magnetic powder material forming the magnetic powder material layer327 is formulated as a material obtained by mixing powder of a magneticmaterial having high permeability, for example powder of an amorphousalloy, with a non-magnetic, non-conductive polymer material, for exampleresin, and is made into a coating material form similarly to themagnetic powder material layer 323 of the first embodiment. The magneticpowder material layer 327 is formed by applying the magnetic powdermaterial having the coating material form in such a manner as to coverthe entire surface, on which the Y-axis-direction loop coil groupconductor 313 is formed, of the insulating substrate 311 of the sensorboard main body 31.

Next, in the second embodiment, a sheet member 328 is obtained byadhering (depositing) the electromagnetic shield layer 324 composed ofaluminum, which is an example of a metal material having low resistanceand high electrical conductivity, on one surface side of the protectivesheet 325. In this case, similarly to the overlay member sheet 32S ofthe first embodiment, an adhesive layer 329 is applied on the topsurface of the electromagnetic shield layer 324 of the sheet member 328and release paper (not shown) is attached to the adhesive layer 329.Then, a roll sheet is obtained by winding the resulting combination intoa roll state.

Then, the release paper of the sheet member 328 drawn out from the rollis peeled off such that the adhesive layer 329 is exposed. Subsequently,the sensor board main body 31, on which the magnetic powder materiallayer 327 has been applied, is disposed on the sheet member 328 and themagnetic powder material layer 327 is bonded to the adhesive layer 329.It should be apparent to those skilled in the art that alignment similarto that of the first embodiment is performed at this point.

Thereafter, similarly to the first embodiment, the sensor board mainbody 31 deposited on the sheet member 328 is subjected to stampingprocessing by a cutter, so that the sensor 5 of the second embodiment isformed.

With the electromagnetic induction sensor 5 of the second embodiment,the same effects as those achieved by the sensor 3 of theabove-described first embodiment are achieved. In addition, because theoverlay base film 321 composed of an insulator is unnecessary, thethickness of the sensor 5 becomes even smaller than that of the sensor 3of the first embodiment.

In the case of the second embodiment, the overlay member for coveringthe Y-axis-direction loop coil group conductor 313 is composed of theprotective sheet 325, the electromagnetic shield layer 324 and themagnetic powder material layer 327, with the protective sheet 325serving as the overlay base film.

Similarly to the above-described first embodiment, the electromagneticshield layer 324 need not be provided also in the sensor 5 of the secondembodiment. Furthermore, the protective sheet 325 may be omitted in bothof the case in which the electromagnetic shield layer 324 is providedand the case in which the electromagnetic shield layer 324 is notprovided.

In the case of omitting the electromagnetic shield layer 324 and theprotective sheet 325, the sensor of the second embodiment can beconfigured by adhering (depositing) the magnetic powder material layer327 on the sensor board main body 31 by coating or the like, as shown inFIG. 8B. In this case, the overlay member consists only of the magneticpowder material layer 327. In the case of omitting only the protectivesheet 325, the overlay member consists of the magnetic powder materiallayer 327 and the electromagnetic shield layer 324.

Other Configuration Examples of Overlay Member

In the above-described second embodiment, the magnetic powder materiallayer 327 is formed on the Y-axis-direction loop coil group conductor313 arranged on a surface of the insulating substrate 311 of the sensorboard main body 31 on the side opposite from the surface sheet side, bydirectly applying the magnetic powder material in a coating materialform over the Y-axis-direction loop coil group conductor 313. However,another method may be employed, in which an overlay member 32A or 32B asshown in FIG. 9A or 9B is prepared and joined to the sensor board mainbody 31.

Specifically, in the overlay member 32A of the example of FIG. 9A, theelectromagnetic shield layer 324 is adhered to the protective sheet 325,and then a magnetic powder material layer 327A is adhered to theelectromagnetic shield layer 324 by coating or the like. Without usingthe overlay base film 321, an adhesive layer 329A is applied to themagnetic powder material layer 327A, and the overlay member 32A isadhered to the sensor board main body 31 by the adhesive layer 329A.

In the overlay member 32B of the example of FIG. 9B, a magnetic powdermaterial layer 327B impregnated with an adhesive is adhered to theelectromagnetic shield layer 324 instead of the magnetic powder materiallayer 327A in the example of FIG. 9A. In the example of FIG. 9B, thesensor board main body 31 and the overlay member 32B can be joinedwithout the adhesive layer 329A, which is necessary in the example ofFIG. 9A.

In these examples of FIGS. 9A and 9B, the overlay base film 321 isunnecessary and omitted as with the above-described second embodiment,and thickness reduction for the whole sensor is possible as with thesecond embodiment.

Further examples of the overlay member are not limited to thosedescribed in FIGS. 9A and 9B. FIG. 9C shows an overlay member 32C of yetanother example. The overlay member 32C of this example is equivalent toa component obtained by removing the protective sheet 325 from theoverlay member 32 of the first embodiment. That is, in the overlaymember 32C of this example, the protective sheet 325 is omitted on theassumption that an object with which the sensor must not be inelectrical contact does not exist on the side opposite from the surfacesheet 314 of the sensor. The adhesive layer 322 is formed on the surfaceof the overlay base film 321 on the side that attaches to the sensorboard main body 31, and the magnetic powder material layer 323 isadhered to a surface of the overlay base film 321 on the opposite side.The electromagnetic shield layer 324 is adhered to the magnetic powdermaterial layer 323. In the overlay member 32C of this example, theelectromagnetic shield layer 324 is exposed.

All of the overlay members 32A, 32B, and 32C of the above-describedexamples are examples that have the overlay base film (protective sheet325 or film 321). Examples to be described below are examples of theoverlay member from which the overlay base film is omitted.

The magnetic powder material layer 323 formed by being applied over theoverlay base film 321, as shown in FIG. 3, can be separated from theoverlay base film 321 after being dried, to thereby form a sheet member.Two examples described below are examples of the case in which themagnetic powder material layer is configured as a sheet member.

An overlay member 32D of the example shown in FIG. 9D does not have theoverlay base film, and includes a magnetic powder material layer 327Dformed as a sheet member. The adhesive layer 322 is formed on thesurface of the magnetic powder material layer 327D on the side thatattaches to the sensor board main body 31, and the electromagneticshield layer 324 is adhered to the surface of the magnetic powdermaterial layer 327D on the opposite side. In the overlay member 32D ofthis example, the electromagnetic shield layer 324 is exposed to theexternal.

An overlay member 32E of the example shown in FIG. 9E does not have theoverlay base film, and includes a magnetic powder material layer 327Eformed as a sheet member. The adhesive layer 322 is formed on thesurface of the magnetic powder material layer 327E on the side thatattaches to the sensor board main body 31, and the overlay member 32Edoes not include the electromagnetic shield layer. In the case of thisexample of FIG. 9E, the magnetic powder material layer 327E formed as asheet member is exposed to the external.

In the overlay members 32D and 32E of the above-described examples ofFIGS. 9D and 9E, even when the thickness of the magnetic powder materiallayer is larger than that of an amorphous alloy layer used in therelated art, due to the omission of the overlay base film composed of,for example, PET, the thickness can be reduced corresponding to thethickness of the overlay base film. Thus, thickness reduction for theentire sensor can be achieved.

Other Embodiments and Modification Examples

In the explanation of the above-described embodiments, a material madeinto a coating material form or a material impregnated with an adhesiveis used as the magnetic powder material. However, the magnetic powdermaterial may be provided as a material obtained by mixing powder of ahigh-permeability amorphous metal or the like with a non-magnetic,non-conductive polymer material, such as resin, and solidifying themixture. It should be apparent to those skilled in the art that theabove-described stamping processing can be similarly performed in thiscase.

Although the number of processing steps is reduced in theabove-described stamping processing, it should be apparent to thoseskilled in the art that the electromagnetic induction sensor of anembodiment of the present invention may be produced similarly to therelated art. For example, a manufacturing method may be used, in whichthe overlay member 32 is subjected to outer shape processing (cut) inadvance and the overlay member 32 that has been subjected to the outershape processing is attached to the sensor board main body 31, which hasbeen separately subjected to outer shape processing.

Furthermore, it should be apparent to those skilled in the art that themethod for joining the overlay member to the sensor board main body 31is not limited to the examples of the above-described embodiments. Forexample, the respective layers and sheets forming the overlay member maybe sequentially deposited to the sensor board main body 31. For example,in the second embodiment, the following method may be employed.Specifically, the magnetic powder material is applied over the surfaceof the insulating substrate 311 of the sensor board main body 31 on theside the Y-axis-direction loop coil group conductor 313 is arranged soas to cover the conductor 313 to thereby form the magnetic powdermaterial layer 327. Thereafter, for example, aluminum that forms theelectromagnetic shield layer 324 is deposited by, for example, pressurebonding or vapor-deposition. The protective sheet 325 is then depositedon the electromagnetic shield layer 324.

In the above-described embodiments, the sensor board main body 31includes the X-axis-direction loop coil group and the Y-axis-directionloop coil group disposed along directions perpendicular to each other.However, the position indicated by the position indicator does not needto be based on two-dimensional coordinates. For example, if it is enoughthat a one-dimensional coordinate can be detected, one loop coil groupmay be disposed only in the one-dimensional coordinate direction.

In the case of disposing a loop coil group only in a one-dimensionalcoordinate direction (e.g. X direction) or in the case of employing aconfiguration in which an alternating magnetic field is generated byonly a loop coil group disposed in a one-dimensional coordinatedirection, it is preferable to set the magnetization direction to adirection that is perpendicular to the thickness direction and is alongthe one-dimensional coordinate direction.

It should be apparent to those skilled in the art that expressions“perpendicular” and “parallel” in the above explanation do not requirebeing strictly perpendicular and being strictly parallel, and insteadencompass states of being almost perpendicular and being almostparallel. That is, it is enough that the magnetic powders contained inthe magnetic powder material layer can be so set that the collectivemagnetization direction of the magnetic powder material layer as a wholeis substantially perpendicular (or almost perpendicular) to thethickness direction.

Although the loop coil group conductors are formed on both surfaces ofthe insulating substrate in the above-described embodiments, it shouldbe apparent to those skilled in the art that the embodiments of theinvention can be applied also in an electromagnetic induction sensor inwhich the loop coil group conductors are formed on only one surface sideof the insulating substrate.

Various modifications, combinations, sub-combinations and alterationsare possible depending on design requirements and other factors based onthe foregoing disclosure within the scope of the appended claims or theequivalents thereof.

What is claimed is:
 1. An electromagnetic induction sensor that is usedwith a position indicator and that includes coils for electromagneticcoupling with the position indicator, the electromagnetic inductionsensor comprising: a sensor board including the coils; and an overlaymember that includes a magnetic powder material layer, the magneticpowder material layer including magnetic powder and defining a layersurface and a thickness direction that extends perpendicularly to thelayer surface, wherein a magnetization direction of the magnetic powderin the magnetic powder material layer extends along the layer surfaceand perpendicularly to the thickness direction of the magnetic powdermaterial layer.
 2. The electromagnetic induction sensor according toclaim 1, wherein the overlay member includes the magnetic powdermaterial layer and a shield material formed of a metal layer, and themagnetic powder material layer is arranged closer to the sensor boardthan the metal layer.
 3. The electromagnetic induction sensor accordingto claim 1, wherein the overlay member further includes an insulator,one surface thereof being applied with an adhesive, and another surfacethereof being applied with the magnetic powder to form the magneticpowder material layer, and said adhesive of the overlay member ispositioned to cover the coils of the sensor board.
 4. Theelectromagnetic induction sensor according to claim 3, wherein theoverlay member still further includes a shield material formed of ametal layer, which is adhered to the magnetic powder material layer. 5.The electromagnetic induction sensor according to claim 1, wherein theoverlay member includes: (i) the magnetic powder applied on the sensorboard to cover the coils, to thereby form the magnetic powder materiallayer, (ii) a shield material formed of a metal layer and attached tothe magnetic powder material layer, and (iii) a protective sheetattached to the shield material.
 6. The electromagnetic induction sensoraccording to claim 5, wherein the shield material is bonded to themagnetic powder material layer by an adhesive.
 7. The electromagneticinduction sensor according to claim 5, wherein the shield material ispressure-bonded to the magnetic powder material layer.
 8. Theelectromagnetic induction sensor according to claim 5, wherein theshield material is vapor-deposited onto the magnetic powder materiallayer.
 9. The electromagnetic induction sensor according to claim 1,wherein the coils for electromagnetic coupling with the positionindicator are composed of a first plurality of loop coils disposed in afirst direction and a second plurality of loop coils disposed in asecond direction perpendicular to the first direction.
 10. Theelectromagnetic induction sensor according to claim 1, wherein themagnetic powder material layer is composed of a mixture materialobtained by mixing the magnetic powder having high magnetic permeabilitywith a polymer material for tuning the high magnetic permeability to apredetermined value.
 11. The electromagnetic induction sensor accordingto claim 10, wherein the mixture material is impregnated with anadhesive.
 12. The electromagnetic induction sensor according to claim10, wherein the polymer material is selected from a group consisting ofresin, rubber, and fiber.
 13. The electromagnetic induction sensoraccording to claim 10, wherein the magnetic powder having the highmagnetic permeability is selected from a group consisting of powder ofan amorphous alloy, powder of permalloy, and powder of ferrite.
 14. Anoverlay member for an electromagnetic induction sensor including asensor board, the sensor board including coils for electromagneticcoupling with a position indicator, the overlay member comprising: amagnetic powder material layer defining a layer surface and a thicknessdirection that extends perpendicularly to the layer surface, wherein amagnetization direction of magnetic powder in the magnetic powdermaterial layer extends along the layer surface and perpendicularly tothe thickness direction of the magnetic powder material layer.
 15. Theoverlay member for the electromagnetic induction sensor according toclaim 14, further comprising a shield material that is formed of a metallayer and is adhered to the magnetic powder material layer.
 16. Theoverlay member for the electromagnetic induction sensor according toclaim 14, further comprising: an adhesive layer having a first surfaceadhered to the magnetic powder material layer and having a secondsurface covered with a release sheet.
 17. A manufacturing method of anelectromagnetic induction sensor, the manufacturing method comprising:providing a sensor board including coils for electromagnetic couplingwith the position indicator; and placing an overlay member that includesat least a magnetic powder material layer over the sensor board, themagnetic powder material layer defining a layer surface and a thicknessdirection that extends perpendicularly to the layer surface, wherein amagnetization direction of magnetic powder in the magnetic powdermaterial layer extends along the layer surface and perpendicularly tothe thickness direction of the magnetic powder material layer.
 18. Themanufacturing method of an electromagnetic induction sensor according toclaim 17, further comprising: stamp-cutting the overlay member placedover the sensor board into a predetermined shape.
 19. The manufacturingmethod of an electromagnetic induction sensor according to claim 17,further comprising: adhering a shield material formed of a metal layerto the magnetic powder material layer to thereby form the overlaymember; and placing the magnetic powder material layer to be closer tothe sensor board than the metal layer.